1. Field of the Invention
This invention generally relates to a centrifugally balanced fluid reservoir and method of use thereof, and more particularly to a centrifugally balanced fluid reservoir that is self-contained, capable of rotation and that regulates the amount of fluid in a rotating device, such as a fluid coupling, viscous clutch, fan drive or other rotating device requiring varying amounts of fluid.
2. Description of Related Art
Fluid couplings and/or viscous clutches are commonly used as part of a rotating power transmission device, wherein the rate of rotation of the output shaft of the fluid coupling is dependant on the characteristics of the coupling, the rotational speed and the amount of fluid within the fluid coupling. The amount of fluid in the fluid coupling can be easily changed when the fluid coupling is not in operation, allowing the rate of rotation of the output shaft to be varied; however, known devices and methods varying the amount of fluid in the fluid coupling during operation are complex, expensive and require a significant amount of maintenance.
The function and use of fluid couplings in rotating power transmission is mature, well defined and widely known. Fluid couplings by design slip internally while shearing the fluid they contain between two semi-toroidal vaned halves, which allows the coupling to transmit torque since there is no mechanical connection between the input and output shafts of the coupling. In general, fluid couplings, for a given input rotational speed and torque transmitted, exhibit higher slip as the fluid level is reduced. Shearing the fluid inside the coupling generates heat in the fluid as a result of the work added to it. The fluid coupling is able to reject the heat generated at the design full load operating point by transferring heat from the coupling's body to the ambient air. This heat transfer is often enhanced by the external design of the coupling with some extended heat transfer surface cooled by the air flow over the coupling created by the spinning motion of the coupling during operation. In general, there is a practical limit to the allowable slip in a fluid coupling in a constant torque application due to the heat rejection to the fluid that results. If the slip and resulting fluid shear is too high, the resulting heat generation overheats the fluid in the coupling and the coupling fails. As a result, existing apparatus' for low fluid level/high slip applications of fluid couplings may consist of a mechanism to constantly exchange the fluid in the coupling via some mechanism to extract the fluid in the coupling and replacing it at the same rate with fresh cool fluid to maintain the desired fluid level within the coupling, thus providing a mechanism of carrying off the heat generated by the fluid shear in this high slip scenario. The hot fluid that is removed is typically cooled by some heat exchange mechanism and then returned to the coupling in a closed loop. The existing apparatus' for this scenario are typically large, complex, expensive, cumbersome, maintenance intensive and impractical for many applications.
It is possible to place a fluid coupling between a rotating power source and a other rotating device requiring varying amounts of fluid. In the case of other rotating device requiring varying amounts of fluids, the torque requirement at reduced speeds diminishes as the square of the reduction in speed. Consequently, the horsepower required diminishes as the cube of the reduction in speed. Using this fact, we have proven to our satisfaction that for
It is therefore desirable to provide a centrifugally balanced fluid reservoir being properly sized and applied to a fluid coupling, viscous clutch or fan drive, wherein the heat rejected by a other rotating device requiring varying amounts of fluid to a fluid coupling in a low fluid level/high slip scenario is no more than is rejected in a full speed/full torque application.
It is further desirable to provide a centrifugally balanced fluid reservoir and method of use thereof that does not require an external heat transfer device to cool the fluid in the coupling, wherein the heat rejected to the ambient air is sufficient to maintain a suitable operating temperature for the coupling.
It is yet further desirable to provide a centrifugally balanced fluid reservoir wherein continuous fluid exchange is not required.
It is yet further desirable to provide a centrifugally balanced fluid reservoir that allows the transfer of fluid from the reservoir to the fluid coupling on an as needed basis, thus achieving a variable speed drive for the other rotating device requiring varying amounts of fluid.
It is yet further desirable to provide a centrifugally balanced fluid reservoir that permits removal of fluid from a rotating device by the centrifugal force inherent to a rotating object. The force created by the fluid in the rotating source is a function of the speed of rotation, the level of fluid in the source, and several other physical properties of the fluid itself.
It is yet further desirable to provide a centrifugally balanced fluid reservoir and method of use thereof whereby regulating the flow from the rotating source counteracts the centrifugal force by an opposing force. The fluid level in the rotating source will naturally seek a balance between the centrifugal force and the opposing force. The fluid in the source will flow into or out of the source until a balance of forces is reached, the source is either empty or full such that it can no longer supply or accept any additional fluid, or the reservoir is either empty or full such that it can no longer supply or accept any additional fluid.
It is yet further desirable to provide a centrifugally balanced fluid reservoir having a fluid reservoir with a variable internal pressure and resulting reservoir volume to modulate the level of fluid in the rotating source.
It is yet further desirable to provide a centrifugally balanced fluid reservoir that allows for easy change in the amount of fluid in a rotating device while the rotating device is in operation.
It is yet further desirable to provide a centrifugally balanced fluid reservoir capable of varying the amount of fluid in a rotating device, such as a fluid coupling, and therefore alter the rate of rotation produced by the rotating device, while the rotating device is in operation.
It is yet further desirable to provide a centrifugally balanced fluid reservoir and method of use thereof that is simple, inexpensive and low-maintenance.
It is yet further desirable to provide a centrifugally balanced fluid reservoir capable of regulating fluid transfer in rotating devices, such as fluid couplings, viscous clutches, fan drives and other rotating devices.